Satellite positioning receivers can determine their position by computing relative times of arrival of signals transmitted simultaneously from satellites such as the U.S. Global Positioning System (GPS) or NAVSTAR satellites. For example, the GPS Orbital Constellation has 28 satellites which orbit the earth in about 12 hour orbits. This constellation provides a satellite positioning receiver with approximately four to twelve satellites visible from any point on earth. These satellites transmit, as part of their message, both satellite positioning data, so-called “ephemeris” data, as well as clock timing data In addition, the satellites transmit time-of-week (TOW) information associated with the satellite signal, which can enable a receiver to determine GPS referenced time at the receiver.
The receiver can determine a location (and accurate time-of day) by searching for and acquiring GPS signals that include the ephemeris and other data for a multiplicity of satellites. The process of searching and acquiring may sometimes require several minutes to complete. In some applications, these several minutes may be unacceptably long, and furthermore, may reduce battery life in portable applications.
It is known to provide GPS time assistance to receivers to reduce the time needed for the receiver to determine a location. In particular, the GPS time assistance can allow the receiver to more accurately predict satellite positions and velocities that can allow the receiver to narrow a frequency search window which can reduce the acquisition time. It is also known to provide GPS time assistance to mobile stations in Global System for Mobile telecommunications (GSM) networks. It is also known to provide GPS time assistance to mobile stations via the Internet using TCP/IP via General Packet Radio Service (GPRS) or any other data service, such as dial-up GSM-data service.